Manufacture of abrasive belts and coated fabrics therefor



A. ACKERMAN 3,013,870

MANUFACTURE OF ABRASIVE BELTS AND COATED FABRICS THEREFOR Dec. 19, 1961Filed June 30, 1958 FIGS.

S RN Y. A E mm MO E 0 mm w A A s H H Y f rm A Unite This inventionrelates to improvements in abrasive materials and the manufacture ofsuch abrasive materials and it relates particularly to improvements incoated webs of woven or felted fabrics formed of natural or syntheticfibers, abrasive sheets and belts made from such fabrics, thecompositions used in the coating of such fabrics and to methods ofmaking the coated fabrics and abrasive sheets and belts.

The manufacture of abrasive cloths and belts for belt sanders and thelike is an old and well known industry and involves certain techniqueswhich are standard in the industry. Usually, the cloths used in themanufacture of abrasive belts are dyed and stretched to the properwidth. 1 Then the back or print surface of the cloth, such as a web ofcotton grey goods is sized with a glue and starch size to fill thespaces between the yarns or fibers and provide a barrier for preventingpenetration of the glue or resin used later for sizing the face side orbonding the abrasive particles or grits to the cloth. Following thesetreatments and after drying of the sizing coats, a layer of a suitableglue such as an animal glue, a synthetic resin glue'or the like isapplied to the face or front surface of the cloth for bonding abrasivegrits to it. Inasmuch as this operation is usually accomplished on acalender roll, the presence of the back and face sizings on the cloth isimportant for the reason that they prevent penetration of the glue forbonding the abrasive grits through the cloth and thereby prevent thecloth from sticking to the calender roll.

Abrasive belts are made from cloth treated as described above byslitting the cloth into strips of a desired width, these strips thenbeing cut, usually on a bias, to a desired length. It is then necessaryto secure the bias-cut ends of the strips together so that they will notseparate when, subjected to the stresses which they encounter in normaluse when operated on a polishing or belt sander. To achieve a strongbond, the abrasive, the glue and other sizing are removed from a narrowzone, usually about wide, at one end of the strip by means of a skivingoperation to expose the fibers of the cloth. Inasmuch as a starch sizehas very little strength, and is not very compatible with the glue usedfor securing the ends of the abrasive strip together, a strong bondcannot be obtained between the skived edge of the strip and the starchsized back. of the strip. Accordingly, it is necessary to remove thesize on the back or print surface of the strip in a zone band aboutwide, at the opposite end of the strip from the skived end. Thisoperation is accomplished by scrubbing, washing or brushing to lay openthe fibers on the back of the cloth. When an adhesive such as an animalglue or synthetic resin glue is applied to the joint, the cleaned zoneon the back surface and the skived, abrasive-free zone on the face ofthe strip will be bonded together strongly without producing anobjectionably thick joint at the zone where the ends of the stripoverlap.

The operation of removing the sizing from the back or print side of thecloth is expensive and time-consuming for the reason that it is donemanually.

In accordance with the present invention, I have pro vided a method andcoating compositions by means of which the porous surfaces of woven offelted fabrics formed of natural or synthetic fibers can be filled torender them especially effective for use in the production of abrasivesheets and belts.

States Patent Patented Dec. 19, 1961 More particularly, a glue sizecontaining a filler of an unusual type has been provided by means ofwhich it is possible to fill a fabric to provide a desired weight andtensile strength necessary for such fabric and to obtain a strong bondbetween the fabric and the abrasive particles thereon. Moreover, thecoating compositions, according to the present invention enable theskived edge of the abrasive coated fabric to be united with the coatedor sized back surface of the fabric without removal of the coating orsize from the back surface of the fabric. In this way, the manualtreatment of the belts prior to gluing their ends together is reducedsubstantially and a joint having increased strength and which can beproduced more economically is obtained.

For a better understanding of the present invention reference may be hadto the accompanying drawing in which:

FIGURES 1 to 3 are schematic illustrations of a typical method embodyingthe present invention;

FIGURE 4 is a plan view of a web of cloth coated with abrasive andillustrating the manner in which the web is cut into narrower strips andon a bias to form abrasive belts;

FIGURE 5 is a plan view of an abrasive belt showing the treatment of oneend thereof; and

FIGURE 6 is a perspective view of a completed abrasive belt made inaccordance with the present invention.

As shown schematically in FIGURES 1, 2 and 3, the abrasive cloth can bemanufactured in a number of operations. As shown in FIGURE 1, a roll 10of fabric 11 formed of woven or felted natural or synthetic fibers oryarns, which has been dyed and stretched to the desired width in theregular procedure used to accomplish this, is fed through a rollercoating apparatus 12 wherein the back or print side of the fabric 11 isfilled with a solution of a suitable glue or resin and a filler of anunusual type further described herein. Thereafter, the fabric 11 withthe back filling is dried by passing it through a suitable dryer 13 androlled up into a roll 14.

As shown in FIGURE 2, the fabric 11 is unwound from the roll 14 and ispassed through a roller coating device 15 which applies a size coatconsisting of a solution of a suitable glue or resin and a filler of anunusual type further described herein. The fabric passes through dryer16 and is wound into roll 17.

While it is preferable that the back filling illustrated in schematicdrawing in FIGURE 1 and the face sizing illustrated in schematic drawingin FIGURE 2 and described herein, be accomplished with one pass throughthe back filling and face sizing roller coating devices, it isunderstood that cloth 11 can be run a number of times through the backfilling and face sizing operations when the specifications call forvarious cloth finishes of such weight and tensile strength that aplurality of passes through the back filling or face sizing operationsare required.

As shown in FIGURE 3, after the cloth is ready for coating, fabric 11 isunwound from the roll 17 and is passed through roller coating device 18which applies a coat of glue or resin to the face side of the clothwhich is compatible with the glue or resin previously applied to thecloth, and thereafter abrasive grain A is deposited by means of ametering device on hopper 19 on the wet glue or resin on the face of thefabric. The fabric is partially dried on a festoon dryer 20, then enterssizing machine 21 which applies a size coat of glue or resin over thegrain on the face side of the cloth, and then the cloth is festoon dried22 and rewound on roll 23.

, Subsequently, the fabric 11 with the abrasive A thereon is cut alonglines 24, 25, 26, etc. to form narrow strips of a desired width. Usuallythe strips are then cut to length on a bias as indicated by the lines 27and 28 in 3 FIGURE 2, to form the individual abrasive strips 29 shown inFIGURE 3. The sizing and coating techniques described above areessentially the same as in the prior methods of manufacture and aresusceptible to considerable modification in the sequence and number ofcoating steps.

In accordance with the present invention, the size applied by thecoating apparatuses 12 and 15 is made up of an animal or synthetic resinglue (hereinafter referred to as glue) containing an inert filler knownas Laminar which imparts increased strength to the glue, forms anexcellent filling for the cloth and also bonds strongly to compatibleglues which are commonly used for securing one end of a strip ofabrasive cloth to the other to form a belt therefrom. Laminar is afinely ground oyster shell product manufactured by Laminar Corporationof Greenwich, Connecticut. The ground oyster shell is composed of thin,fiat, irregularly shaped flakes or leaves having an average particlesize of about one and one-half to seven microns. These flaky or leaflikeparticles readily fill the interstices between the fibers and the yarnsmaking up the cloth and cover the cloth, thereby forming a barrier tothe penetration of the glue by means of which the abrasive grits arebonded to the face of the cloth. Several grades of Laminar areavailable. In one grade 98 /2% of the particles are smaller than micronsand 32% to 34% are smaller than one micron. In another grade 100% of theparticles are smaller than 35 microns and 12% to are smaller than onemicron. Either grade is satisfactory and in practice, the largerparticle sizes are preferred, principally on the basis of manufacturingeconomy. Inasmuch as the particles are thin and flaky, they form anoverlapping shingle or scale-like layer which has excellent coveringpower and in which the particles are strongly bonded togcther by thethin layers of glue between the overlapping faces of the particles. Ithas been found that one pound of Laminar has a surface area of over .6of an acre,

A typical sizing composition for back sizing the cloth 11 in the coatingapparatuses 12 and 15 is composed of:

Lbs. Animal glue (dry weight), 114 millipoises 35 Laminar 40 Water 65Another suitable size for back sizing the fabric 11 has the followingcomposition:

Lbs. Animal glue (dry weight), 86 millipoises 40 Laminar 80 Water 65 Asuitable size for face sizing the fabric in formation is as follows:

Lbs. Animal glue (dry weight), 114 millipoises 35 Laminar 35 Water 65 Itwill be understood that an equivalent proportion of a synthetic resinglue may be substituted for the animal glue in each of the precedingsizing compositions.

A suitable animal glue is hide glue. Suitable synthetic resin glues arethe vinyl, melamine, polyester, phenolformaldehyde and urea resins. Itwill be understood that best results are obtained when the sizes andother coatings applied to the fabric contain the same kind of glues, or,in any event, glues which are compatible with each other.

Moreover, the proportion of Laminar can be varied considerably. Aslittle as one part of Laminar to one part of dry glue by weight or asmuch as three parts of Laminar to one part of dry glue by weight can beused. Also the amount of water can be varied depending on the desiredviscosity of the sizing composition.

It has also been found helpful to include aproportion 4 of Laminar inthe glue applied from the glue fountain 18 inasmuch as the fillerstrengths the glue and affords a very strong bond between the abrasivegrits and the cloth 11. Typical glues for this operation are disclosedmore particularly in the Gustaf A. E. Ackerman application Serial No.462,614, filed October 15, 1954.

One end of the abrasive coated strip 29 is subjected to a skivingoperation to remove the abrasive grits, the glue and the size from anarrow zone 30 at one end of the strip, thereby to expose the fibers andrender them receptive to glue which is used to secure the opposite endsof the strip together to form an abrasive belt 31, like that shown inFIGURE 4. Inasmuch as the back or print surface of the strip 29 has acoating of glue containing Laminar, it is completely compatible with asimilar glue which is applied to the skived zone 30 of the strip 29.Therefore, when the print surface at one end of the belt is brought intooverlapping relation to the skived zone 30 of the strip 29 with ananimal or synthetic resin glue applied thereto and the overlapping edgesare subjected to heat and pressure, a very strong and durable bond isobtained between the overlapping edges.

Belts 31 of a type described herein operate for prolonged periods oftime without failure of the bond between the ends of the abrasive stripeven when used for polishing metal castings and the like. In suchpolishing operations, the belts are normally subjected to a tension ofabout 70 pounds or more when installed in the polishing machine. Greatertensile stresses are exerted on the belt and the joint between itsoverlapped and glued edges during polishing because of deflection of thebelt by the pressure applied by the castings.

It will be understood that the process is susceptible to considerablevariation in the sequence or order of steps of sizing, glue dipping andthe like.

Moreover, the proportions of Laminar used in the various sizingoperations can be varied considerably but should not be appreciably moreor less than the proportions indicated above if optimum results are tobe achieved.

From the foregoing, it will be understood that the examples of thesizing compositions are illustrative and should not be considered aslimiting the scope of the following claims.

I claim:

1. A method of making abrasive belts comprising sizing one side of a webof fabric with a glue sizing containing flaky ground oyster shellparticles having an average particle size of about one and one-half toseven microns, adhering an abrasive grit to the other side of saidfabric, cutting said fabric into strips, removing the abrasive grit fromone end of a strip and gluing said one end of said strip directly to thesized side of said strip to form an endless belt.

2. A method of making abrasive belts comprising sizing one side of a webof fabric with a liquid glue sizing composition containing flaky groundoyster shell particles having an average particle size of about one andone-half to seven microns, said ground oyster shell particles beingpresent in an amount between about one part to about three parts toabout one part of dry glue, by weight, adhering an abrasive grit to theother side of said fabric, cutting said fabric into strips, removing theabrasive grit from one end of a strip and gluing said one end of saidstrip directly to the sized side of said strip to form an endless belt.

3. A method of coating fabrics comprising back-sizing one side of a webof fabric with a liquid glue sizing composition containing flaky groundoyster shell particles having an average particle size of about one andone-half to seven microns as a filler, said ground oyster shellparticles being present in an amount not substantially exceeding aboutthree parts by weight to about one part by weight of dry glue.

4. A method of making abrasive belts comprising sizing one side of a webof fabric with a liquid glue sizing composition containing flaky groundoyster shell particles having an average particle size of about one andone-half to seven microns as a filler, said ground oyster shellparticles being present in an amount not substantially exceeding aboutthree parts by weight to about one part by weight of dry glue, adheringan abrasive grit to the other side of said web, cutting said web intostrips, removing the abrasive grit from one end of a strip and gluingsaid one end of said strip directly to the sized side of said strip toform an endless belt.

5. A method of making abrasive belts comprising sizing one side offabric with a liquid glue sizing composition containing flaky groundoyster shell particles having an average particle size of about one andone-half to seven microns, said ground oyster shell particle beingpresent in an amount of about 40 to 80 parts by weight to about 35 to 40parts by weight of dry glue, drying the sized fabric; sizing theopposite side of said fabric with a liquid glue sizing compositioncontaining ground oyster shell particles having an average particle sizebetween about one and one-half and seven microns, and adhering anabrasive grit to said opposite side of said fabric, the dry glue beingpresent in about equal amounts by weight.

6. A method of making abrasive belts comprising sizing one side offabric with a liquid glue sizing composition containing flaky groundoyster shell particles having an average particle size of about one andone-half to seven microns, said ground oyster shell particle beingpresent in an amount of about 40 to 80 parts by weight to about 35' to40 parts by weight of dry glue, drying the sized fabric; and sizing theopposite side of said fabric with a liquid glue sizing compositioncontaining ground oyster shell particles having an average particle sizebetween about one and one-half and seven microns, said ground oystershell particles being present in an amount of about forty parts byweight to about twenty-five parts by weight and dry glue being presentin about equal amounts by weight; adhering an abrasive grit to the otherside of said fabric, removing the abrasive grit from one end of a stripof said fabric, to expose a part of said other surface of said fabric,and gluing said one end of said strip directly to the sized surface atthe other end of said strip to form an endless belt having abrasivegrits on its outer surface.

7. An abrasive belt comprising a strip of fabric having abrasive gritbonded to its outer surface, the opposite side of said strip having aglue size thereon containing flaky ground oyster shell particles havingan average particle size of about one and one-half to seven microns,filling the interstices of said fabric, one end of said strip being freeof said abrasive grit and being glued directly to the side of the fabrichaving the glue size thereon in overlapping relation thereto.

8. An abrasive belt comprising a strip of fabric having abrasive gritbonded to its outer surface, the opposite side of said strip having aglue size thereon containing flaky ground oyster shell particles havingan average particle size of about one and one-half to seven microns,said ground oyster shell particles being present in an amount betweenabout one and three parts by weight to about one part of dry glue byweight filling the interstices of said fabric, one end of said stripbeing free of said abrasive grit and being glued directly to the side ofthe fabric having the glue size thereon in overlapping relation thereto.

9. An abrasive belt comprising a strip of fabric having abrasive gritbonded to its outer surface, the opposite side of said strip having aglue size thereon containing flaky ground oyster shell particles havingan average particle size of about one and one-half to seven microns,said ground oyster shell particles being present in an amount of aboutone to three parts by weight to about one part of dry glue by weight andfilling the interstices of said fabric, one end of said strip being freeof said abrasive grit and being glued directly to the side of the fabrichaving the glue size thereon in overlapping relation thereon.

10. An abrasive belt comprising a strip of fabric having abrasive gritbonded to one surface by a glue, the opposite side of said strip havinga glue size thereon containing flaky ground oyster shellparticles'having an average particle size of about one and one-half toseven micron filling the interstices in said cloth, a narrow zone at oneend of said strip being substantially free of gut and being glueddirectly to the sized side of the other end of said strip in overlappingrelation thereto.

11. Fabric for abrasive belts'and sheets consisting essentially of astrip of fabric having a glue back-filling size thereon containing flakyground oyster shell particles having an average particle size of aboutone and onehalf to seven microns, said ground oyster shell particlesbeing present in an amount of about one to three parts by weight toabout one part of dry glue by weight and filling the interstices of saidfabric.

12. Fabric for abrasive belts and sheets consisting essentially of astrip of fabric having a glue back-filling size thereon containing flakyground oyster shell particles having an average particle size of aboutone and one-half to seven microns filling the interstices in saidfabric.

13. Fabric for abrasive belts and sheets consisting essentially of astrip of fabric having on its opposite sides a glue size thereoncontaining flaky ground oyster shell particles having an averageparticle size of about one and one-half to seven microns, said groundoyster shell particles being present in an amount of about one to threeparts by weight to about one part of dry glue by weight, the glue sizefilling the interstices of said fabric.

References Cited in the file of this patent UNITED STATES PATENTS2,322,154 Oglesby June 15, 1943 2,431,035 Goepfert et al. Nov. 18, 19472,794,726 Riedesel et al. June 4, 1957 2,873,181 Hanford Feb. 10, 1959

9. AN ABRASIVE BELT COMPRISING A STRIP OF FABRIC HAVING ABRASIVE GRITBONDED TO ITS OUTER SURFACE, THE OPPOSITE SIDE OF SAID STRIP HAVING AGLUE SIZE THEREON CONTAINING FLAKY GROUND OYSTER SHELL PARTICLES HAVINGAN AVERAGE PARTICLE SIZE OF ABOUT ONE AND ONE-HALF TO SEVEN MICRONS,SAID GROUND OYSTER SHELL PARTICLES BEING PRESENT IN AN AMOUNT OF ABOUTONE TO THREE PARTS BY WEIGHT TO ABOUT ONE PART OF DRY GLUE BY WEIGHT ANDFILLING THE INTERSTICES OF SAID FABRIC, ONE END OF SAID STRIP BEING FREEOF SAID ABRASIVE GRIT AND BEING GLUED DIRECTLY TO THE SIDE OF THE FABRICHAVING THE GLUE SIZE THEREON IN OVERLAPPING RELATION THEREON.